Numerical modeling of geothermal reservoir in unsaturated environment (Case study: Geothermal field northwest of Sabalan)

In this research, firstly, a conceptual model designed of ten deep exploratoration wells has been developed, and based on this, a three-dimensional numerical model of the North-West Sablan geothermal system has been presented. For this purpose, the EOS3 module (water-air equation) of the Tough2 simulator code was used to simulate the model. The numerical model of the reservoir is expressed by a rectangular prism with a length of 11.5 km, a width of 8 km (92 km2) and a depth of 5.11 km, and it was expanded with 21 horizontal layers with a thickness range of 100 to 1000 meters from the maximum altitude of 4110 to -1000 masl. The number of 22 rock-types, whose distribution is based on the distribution of rock units and geological structures in 10 deep exploratory wells, was assigned to the model. The permeability of the rock types varies from 1*10E-17 to 9*10E-13 square meters. Modeling was done for the natural state of the reservoir and the validation results showed a good match between the data measured in the well and modeled for temperature and pressure. In the best fit, the simulation provided a zone of high temperature upward flow in the southeastern part of the range (sites D and E). This flow is transferred through permeable, faulted and fractured zones and is finally discharged through surface features (hot water springs) in the northwestern part of the area.